/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_sub_q15.c
 * Description:  Q15 vector subtraction
 *
 * $Date:        18. March 2019
 * $Revision:    V1.6.0
 *
 * Target Processor: Cortex-M cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the License); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "arm_math.h"

/**
  @ingroup groupMath
 */

/**
  @addtogroup BasicSub
  @{
 */

/**
  @brief         Q15 vector subtraction.
  @param[in]     pSrcA      points to the first input vector
  @param[in]     pSrcB      points to the second input vector
  @param[out]    pDst       points to the output vector
  @param[in]     blockSize  number of samples in each vector
  @return        none

  @par           Scaling and Overflow Behavior
                   The function uses saturating arithmetic.
                   Results outside of the allowable Q15 range [0x8000 0x7FFF] are saturated.
 */

#if defined(ARM_MATH_MVEI)

#include "arm_helium_utils.h"

void arm_sub_q15(
	const q15_t *pSrcA,
	const q15_t *pSrcB,
	q15_t *pDst,
	uint32_t blockSize)
{
	uint32_t  blkCnt;           /* loop counters */
	q15x8_t vecA;
	q15x8_t vecB;

	/* Compute 8 outputs at a time */
	blkCnt = blockSize >> 3;
	while (blkCnt > 0U) {
		/*
		 * C = A - B
		 * Subtract and then store the results in the destination buffer.
		 */
		vecA = vld1q(pSrcA);
		vecB = vld1q(pSrcB);
		vst1q(pDst, vqsubq(vecA, vecB));
		/*
		 * Decrement the blockSize loop counter
		 */
		blkCnt--;
		/*
		 * advance vector source and destination pointers
		 */
		pSrcA  += 8;
		pSrcB  += 8;
		pDst   += 8;
	}
	/*
	 * tail
	 */
	blkCnt = blockSize & 7;
	if (blkCnt > 0U) {
		mve_pred16_t p0 = vctp16q(blkCnt);
		vecA = vld1q(pSrcA);
		vecB = vld1q(pSrcB);
		vstrhq_p(pDst, vqsubq(vecA, vecB), p0);
	}
}


#else
void arm_sub_q15(
	const q15_t *pSrcA,
	const q15_t *pSrcB,
	q15_t *pDst,
	uint32_t blockSize)
{
	uint32_t blkCnt;                               /* Loop counter */

#if defined (ARM_MATH_LOOPUNROLL)

#if defined (ARM_MATH_DSP)
	q31_t inA1, inA2;
	q31_t inB1, inB2;
#endif

	/* Loop unrolling: Compute 4 outputs at a time */
	blkCnt = blockSize >> 2U;

	while (blkCnt > 0U) {
		/* C = A - B */

#if defined (ARM_MATH_DSP)
		/* read 2 times 2 samples at a time from sourceA */
		inA1 = read_q15x2_ia((q15_t **) &pSrcA);
		inA2 = read_q15x2_ia((q15_t **) &pSrcA);
		/* read 2 times 2 samples at a time from sourceB */
		inB1 = read_q15x2_ia((q15_t **) &pSrcB);
		inB2 = read_q15x2_ia((q15_t **) &pSrcB);

		/* Subtract and store 2 times 2 samples at a time */
		write_q15x2_ia(&pDst, __QSUB16(inA1, inB1));
		write_q15x2_ia(&pDst, __QSUB16(inA2, inB2));
#else
		*pDst++ = (q15_t) __SSAT(((q31_t) * pSrcA++ - *pSrcB++), 16);
		*pDst++ = (q15_t) __SSAT(((q31_t) * pSrcA++ - *pSrcB++), 16);
		*pDst++ = (q15_t) __SSAT(((q31_t) * pSrcA++ - *pSrcB++), 16);
		*pDst++ = (q15_t) __SSAT(((q31_t) * pSrcA++ - *pSrcB++), 16);
#endif

		/* Decrement loop counter */
		blkCnt--;
	}

	/* Loop unrolling: Compute remaining outputs */
	blkCnt = blockSize % 0x4U;

#else

	/* Initialize blkCnt with number of samples */
	blkCnt = blockSize;

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */

	while (blkCnt > 0U) {
		/* C = A - B */

		/* Subtract and store result in destination buffer. */
#if defined (ARM_MATH_DSP)
		*pDst++ = (q15_t) __QSUB16(*pSrcA++, *pSrcB++);
#else
		*pDst++ = (q15_t) __SSAT(((q31_t) * pSrcA++ - *pSrcB++), 16);
#endif

		/* Decrement loop counter */
		blkCnt--;
	}

}
#endif /* defined(ARM_MATH_MVEI) */

/**
  @} end of BasicSub group
 */
